Image Sensor Readout Circuit with Dynamic Amplification Selection
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Solution Overview
Problem
Existing image sensors have a limited dynamic range, leading to spatial distortions and image quality issues when trying to increase dynamic range by combining images with different exposure times, and adding additional channels for higher dynamic range results in increased design effort and costs.
Innovation Solution
An image sensor with a readout circuit that selects from three different amplification factors for each pixel, allowing for the output of only the necessary amplified signals, reducing the number of channels and components required, and using a selection device to determine the appropriate amplification factors based on signal levels for improved signal-to-noise ratio and dynamic range without significant additional design effort or costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple channels with different amplification factors are added to increase dynamic range, then the dynamic range and signal-to-noise ratio are improved, but the device complexity and manufacturing costs increase
Solution Approach 1:
The patent implements a dynamic selection mechanism where a selection device chooses between multiple amplification factors based on the input signal level. This allows the system to adaptively optimize the signal-to-noise ratio for different exposure conditions without requiring all channels to be active simultaneously, thereby improving reliability while controlling complexity.
Solution Approach 2:
The patent changes the amplification parameter dynamically by selecting from multiple amplification factors (e.g., first, second, and third amplification factors) based on signal level thresholds. This parameter change approach allows the system to achieve varying degrees of amplification without adding permanent hardware complexity for all possible amplification levels.
2Reliability
If multiple channels with different amplification factors are added to increase dynamic range, then the dynamic range is improved, but the manufacturing costs increase
Solution Approach 1:
The dynamic selection of amplification factors based on signal levels allows the system to achieve extended dynamic range without permanently implementing all possible amplification channels. This reduces manufacturing complexity and costs while maintaining the capability to operate across a wide dynamic range when needed.
Solution Approach 2:
By implementing parameter changes in the amplification factor selection rather than hardwiring multiple permanent channels, the system achieves extended dynamic range with reduced manufacturing complexity. The selection device enables flexible parameter adjustment without requiring all amplification paths to be physically present.
3Reliability
If images with different exposure times are combined to increase dynamic range, then the dynamic range is improved, but spatial distortion occurs due to temporal separation
Solution Approach 1:
The patent applies preliminary amplification to the pixel signals before readout, with different amplification factors selected based on expected signal levels. This preliminary action allows the system to capture adequate signal strength for low-exposure regions without requiring separate exposure passes, thereby maintaining spatial consistency while extending dynamic range.
Solution Approach 2:
By changing the amplification parameter based on signal level thresholds, the system can enhance weak signals from low-exposure pixels without requiring separate exposure captures. This parameter adjustment occurs within the same exposure timing, preventing spatial distortion while achieving extended dynamic range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the dynamic range and signal-to-noise ratio of image sensors while minimizing additional design complexity and costs, providing a cost-effective method to achieve improved image quality by selectively amplifying signals based on pixel levels.
Implementation Method 1
light-sensitive elements—so-called pixels—arranged in particular in rows and columns, which convert light falling through a lens of the camera into electrical signals
Data Source
Figure 1a~1b
Figure 2
Figure 3a
AI summary
The sensor (1) has a selection circuit (4) with an amplifier for amplifying signals of light-sensitive pixels (2) with different amplification factors to produce different amplified signals, and an output that outputs the signals as output signals. Three different amplification factors are selectable for signal of respective pixel. The circuit has a selective device for selecting amplification factors depending on height of signal of respective pixel to amplify the output signals. The number of output signals amounts to two and is lesser than the number of selectable amplification factors. An independent claim is also included for a method for selecting an image sensor.